Genetic Estimates for Growth and Shape-Related Traits in the Flatfish Senegalese Sole

Abstract

Shape quality is very important in flatfish aquaculture due to the impact on commercialization. The Senegalese sole (Solea senegalensis) is a valuable flatfish with a highly elliptic body that slightly changes with age and size, and it is prone to accumulating malformations during the production cycle. The present study aims to investigate the genetic parameters of two growth traits (weight and standard length) and six shape quality predictors (ellipticity, three body heights (body height at the pectoral fin base [BHP], body maximum height [BMH] and caudal peduncle height [CPH]) and two ratios (BMH/BHP and BMH/CPH)). These traits were measured before the on-growing stage (age ~400 days (d)) and at harvest (~800 d). Phenotypic data, heritabilities and genetic and phenotypic correlations between the traits are presented and discussed. High or very high heritabilities (0.433-0.774) were found for growth traits, body heights and ellipticity and they were higher at 400 than 800 d. In contrast, the ratios of BMH/BHP and BMH/CPH were less heritable (0.144-0.306). Positive and very high (>0.95) correlations between growth traits and the three heights were found and decreased with age. In contrast, ellipticity had negative and medium-high genetic correlations with growth traits and heights, indicating fish selected for bigger size would also become rounder. The ratio of BMH/CPH showed low genetic correlations with all traits and provided complementary information to ellipticity for a better fitting to the expected lanceolate body morphology of sole. The genetic correlations for all traits at both ages were very high, indicating that selection before entering the growth-out stage in recirculation aquaculture systems is recommended to accelerate genetic gains.

Keywords: Senegalese sole; breeding; genetic estimates; growth; shape.

Figure 1

Shape measurements: 1: standard length (SL); 2: body height at the insertion of the pectoral fin (BHP); 3: body maximum height (BMH); 4: caudal peduncle height (CPH); and 5: ellipticity ((SL − BMH)/(SL + BMH)). A theoretical ellipse fitting the horizontal axis from the mouth tip to the peduncle center and the vertical axis to BMH is indicated by red dashed line.

Figure 2

Estimated marginal means for weight and standard length (SL) as determined by repeated-measures ANOVA at 400 and 800 days (d) for (A) gender (male: M; female: F), (B) Evaluation Batch (EB) (1–7) and (C) Amoebic disease (AD) (infected: I; non-infected: NI). The asterisks (*) on the horizontal or vertical arrows denote if within- or between-subject effects were significant.

Figure 3

Estimated marginal means for height at the pectoral fin base (body height at the insertion of the pectoral fin (BHP), body maximum height (BMH) and caudal peduncle height (CPH) as determined by repeated-measures ANOVA at 400 and 800 days (d) for (A) gender (male: M; female: F), (B) Evaluation Batch (EB) (1–7) and (C) Amoebic disease (AD) (infected: I; non-infected: NI). The asterisks (*) on the horizontal or vertical arrows denote if within- or between-subject effects were significant.

Figure 4

Violin plots for body maximum height (BMH) to caudal peduncle height (CPH) and BMH to body height at the insertion of the pectoral fin (BHP) ratios. Data for males (M) and females (F) at both 400 and 800 days (d) are indicated. The asterisk (*) denotes statistically significant differences between ages.

Figure 5

Distribution of ellipticity classes by weight. Panels (A) (400 days (d)) and (B) (800 d) show the frequency of males (green) and females (red) by ellipticity classes. Panels (C) (400 d) and (D) (800 d) show the ellipticity scatterplot by weight class and gender. The asterisks (*) denote statistically significant differences between gender in a weight class.

Figure 6

Estimated marginal means for ellipticity as determined by repeated-measures ANOVA at 400 and 800 days (d) for the (A) gender (male: M; female: F), (B) Evaluation Batch (EB) (1–7) and (C) Amoebic disease (AD) (infected: I; non-infected: NI). The asterisks (*) on the horizontal or vertical arrows denote if within- or between-subject effects were significant.